1. Field of the Invention
The present invention is related to a novel oxetane compound, an active energy ray-curable compound including the oxetane compound, an active energy ray-curable compound including the oxetane compound, and an inkjet recording method.
2. Description of the Related Art
Image recording methods that form an image on a recording medium such as paper based on image data signals, include electrophotographic systems, sublimation type and melt type heat transfer systems, inkjet systems and the like. The electrophotographic systems require a process of forming an electrostatic latent image on a photoreceptor drum by means of electrical charging and exposure, and thus there are problems such as complicated systems, and consequent increases in the production cost. The heat transfer systems employ inexpensive apparatuses, but since the systems make use of ink ribbons, there are problems such as high running cost and the generation of waste materials. On the other hand, the inkjet systems employ inexpensive apparatuses, and since the systems perform image formation directly on a recording medium, by jetting ink only on those image areas where necessary, an efficient use of the ink can be made at low running cost. Furthermore, the inkjet systems produce less noise, and work excellently as an image recording system.
As an inkjet ink having printing adaptability to non-absorptive recording media such as plastics, there are known ultraviolet (UV)-curable inks that cure upon irradiation with ultraviolet radiation (see, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 9-183927 and 2003-292855). UV-curable inks have an advantage that the time or facilities to volatilize organic solvents are not required, as compared with solvent-based inks When such a UV-curable ink is used, systems utilizing radical polymerization of monomer components are generally used for the curing.
In recent years, ultraviolet curable inkjet inks in which a cationic polymerizable compound is used have also been proposed. However, it is not still easy to design an ink which has excellent curability and the viscosity of which is sufficiently low, whereby stable jetting is enabled. In order to address these issues, oxetane compounds having a specific structure have been proposed. That is, an inkjet ink including an oxetane compound which has a p-methoxyphenyl group at a carbon atom that is adjacent to the oxygen atom included in the oxetane ring, has been proposed (see JP-A No. 2001-181386). However, since this compound is a monofunctional compound, sufficient curability may not be attained, and the compound may be remained unreacted, which may cause safety issues. Further, a bifunctional compound of such an oxetane compound has also been reported (see, JP-A No. 2005-2166); however, since the molecular weight of such a compound is large, the viscosity may be higher and, further, when such a compound is used for an inkjet ink, jetting stability may be an issue to concern.
As such, in conventional cationic polymerizable curable compositions that are used in, for example, curable ink compositions, sufficient curing sensitivity and strength of cured film has still not been attained yet. Further, when such a conventional cationic polymerizable curable composition is used in an inkjet ink, there is a room for improvement from the viewpoint of jetting stability.